Hey there.

Downloaded the installer twice already (with GOG's downloader) and everytime I get this error:

blablabla\voice.cmp

(...) source file is corrupted.

I could try and see what happens if I simply ignore this issue, but I want a stable and complete installation.

So what should I do? And why are GOG's installation files broken?

Thanks in advance.

Do not use GoGs downloader client, it caused me so many problems I just stopped using it.

The GOG downloader has no such problems -- I, and countless others, have never had corrupted downloads. At least that's the case in Windows.

I did not say it did have such problems, I do not know if I would have gotten a corrupt files or not, I have never managed to get it to download anything on my Mac, I had different problems with it each time I tried it.

Yes you did. Quote:
"Do not use GoGs downloader client, it caused me so many problems"

Advising somebody not to use it just because you experienced issues is a touch harsh. It may not have been the downloader that actually cause you issues.